Since mankind undertook the construction of buildings, people have devised various ways to elevate workers to work on surfaces that they could not reach standing on the floor or the ground. For many years, various forms of scaffolding have been known as a mechanism for providing elevated surfaces upon which people can work. Scaffolding possesses the general advantages of relative stability and the ability to significantly elevate the worker. It is well known that one of the fundamental disadvantages of scaffolding is the difficulty of moving same horizontally. In order to provide horizontal movement (i.e., in a plane parallel to the ground or floor) of the worker, the scaffolding must be made larger, or else smaller sections of scaffolding must be moved, a job which often requires disassembly. Step ladders have the advantage of relative ease of movement but they allow very little horizontal movement while the worker is mounted on the ladder due to the danger of taking the worker's center of gravity outside the footing of the ladder.
Workers who need to be elevated, particularly those finishing sheet rock on the ceilings of residential buildings, have come to use what are known as utility stilts or sheetrocker's stilts. Such stilts are constructed in the form of an elongated parallelogram with a high friction pad or shoe at the bottom and a boot or other receptacle for a person's shoe at the top. The parallelogram is normally spring loaded to allow some flexing in the manner of a parallel linkage, but is semi rigid and strongly loaded so that the worker will not fall. An example of sheetrocker's stilts may be seen in the disclosure of U.S. Pat. No. 4,255,822 to Dixon.
While sheetrocker's stilts have great utility and are commonly used throughout the United States, they have several drawbacks. First, the stilts are expensive, currently costing around $250 to $300 U.S. per pair. There is a fairly long learning curve for learning how to comfortably use sheetrocker's stilts. Additionally, because of their construction, it is necessary to assure that the feet of the user are tightly and securely bound to the top platform of the stilts. This normally leads to a relatively time consuming and laborious task of securing the boots or shoes of the user to the upper platforms of the stilts. Once the user has mounted the stilts and succeeding in standing upright, the stilts provide great lateral mobility. However, the task of dismounting the stilts is time consuming. Also, it is very beneficial to have the assistance of a wall or elevated surface for temporary support as the user lowers himself or herself to the ground to dismount the stilts.
As many sheetrockers know, dropping a tool while mounted on sheetrocker stilts is extremely annoying because of the physical labor involved and the time consumed in dismounting the stilts to retrieve the tool and remounting them via a complementary operation.
Thus, there have been some fundamental tradeoffs involved in using the worker elevation devices of the prior art. Generally, there is a tradeoff between vertical and lateral mobility. Conventional sheetrocker's stilts provide good lateral mobility to the worker. However, it is a difficult and laborious job to mount and dismount the stilts. Therefore, vertical mobility is limited. As noted above, problems such as the dropping of tools, or the need to temporarily suspend work, for example, to visit the restroom, can be annoying inconveniences that result from the lack of vertical mobility when using such stilts.
On the other hand, scaffolding provides good vertical mobility in that it is easy to mount and dismount scaffolding vertically. However, in order to provide lateral mobility, the movement of the scaffolding and disassembly and reassembly of same is problematic. In order to provide both, large arrays of scaffolding must be built which inhibit the ability of other workers to move through and work in the area occupied by the scaffolding.
The prior art has developed other forms of stilt and jack devices for elevating workers. For example, U.S. Pat. No. 1,930,363 to Knox shows a pair of jacks that elevate a worker. However, they provide only a modest increase in elevation.
U.S. Pat. No. 2,292,074 to Hawk shows what it calls a "foot scaffold". It provides a relatively stable wide footing and significant elevation. However, the mounting of same, particularly raising one's self to the elevated position using such a device, appears difficult.
U.S. Pat. No. 1,190,421 to Kalcy shows a jack device with a boot on top. There is an elongated handle for operating a pawl which raises a rectangular frame connected to a rack. This allows the user to jack himself up or down. However, the footprint of each such jack is only nominally larger than the footprint of the user's shoe. Also, U.S. Pat. No. 1,905,112 shows a fruit picker's stilt with an elongated arcuate rocker foot.
There is a need in the art to overcome the fundamental tradeoffs cited above. In particular, there is a need for a worker elevating device which provides the lateral mobility of sheetrocker stilts but still allows the worker to mount and dismount relatively quickly. Additionally, it is desirable to have such a device provide elevation that is comparable to that achieved with conventional sheetrocker stilts to allow sheetrock finishing work to be done on conventional residential housing as it is currently built in the United States of America. It is desirable that such a device be lightweight and relatively inexpensive, yet provide a stable and mobile working surface.